1. The Field of the Invention
The present invention relates to an input device of 3-D translation and rotation and its method used for inputting 3-D translation and rotation to a data processing system such as a computer or to an amusement system.
2. The Relevant Technology
Recently, with an increase in processing speed of computers and development in computer graphics (CG) technique, 3-D input technique has been finding wide application in various fields rapidly. In particular, demand for 3-D input devices sharply increases in applications in the Internet typified by consumer entertainment systems or VRML (Virtual Reality Modeling Language). In computer graphic design or CAD systems, a mouse or tablet is very popular as an input device. In addition, to carry out manipulation, observation and modification of object models from an arbitrary direction, demand for inexpensive devices for viscerally inputting 3-D translation and rotation is escalating.
Today, there are various types of 3-D input devices such as those based on the measurement of magnetic fields, photometric stereo and acoustic time-of-flight, and a joystick. The devices based on the measurement of magnetic fields and photometric stereo carry out desired measurement of translation and rotation using a transmitter and receiver. The joystick includes a precision mechanical link to convert its movement to 3-D position information. The photometric stereo obtains 3-D position information from information of parallax using multiple TV cameras.
In addition, a device is proposed which employs four photo detectors and a display unit to obtain translation and rotation of the photo detectors (see, Japanese Patent Application Laid-open No. 9-325007 (1997), for example). The device utilizes the calculation method disclosed in Japanese Patent Application Laid-open No. 7-270124 (1995), enabling 3-D measurement with an inexpensive lens and a small number of photo devices. Since this method carries out 3-D measurement optically, it can achieve stable 3-D input without any effect of magnetic field or temperature.
Since the conventionally available 3-D input device based on the measurement of magnetic field measures variations in spatial magnetic field, it is vulnerable to metallic parts, electronic devices and geomagnetism. On the other hand, since the acoustic time-of-flight device measures the phase or time-of-flight of sonic waves, it is vulnerable to atmospheric pressure or temperature. In addition, both of them require a transmitter and receiver, thereby increasing the device size. Furthermore, since the joystick must carry out translation and rotation independently, it is inappropriate as a visceral 3-D input device.
Finally, since the 3-D input device employing the four photo detectors and display unit (Japanese Patent Application Laid-open No. 9-325007 (1997), for example) has a minimum number of photo detectors necessary, even omission of a single detection point on the display disables the 3-D measurement. Furthermore, since the calculation method disclosed in Japanese Patent Application Laid-open No. 7-270124 (1995) markedly reduces its sensitivity when the display surface directly faces the photo detectors, or when a line connecting parallel two of the four photo detectors is parallel to the display surface at the photo receiving side, the device is limited in its application. Moreover, since the 3-D measurement cannot be carried out until the detection of all the four photo detectors has been complemented, the 3-D measurement interval is limited to within the interval between the scanning time of the display unit.